Fix failing MetricsWebContentsObserverTest with BackForwardCache

This CL fixes all the MetricsWebContentsObserverTest which
checks for ERR_NO_IPCS_RECEIVED event during deletion of page after
navigating away. As with BFCache, page is kept alive after navigating.

ERR_NO_IPCS_RECEIVED is logged during desturction of a page
which happens when page navigates away. But with BackForwardCache,
page is stored in back-forward cache.

We also add BackForwardCache::IsBackForwardCacheFeatureEnabled()
to //content/public to check if BackForwardCache is enabled or not.

Bug: 1157426
Change-Id: I989a033f55a7f626b426c3c013c136f00f35e704
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2611007Reviewed-by: Hajime Hoshi <hajimehoshi@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Sreeja Kamishetty <sreejakshetty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840969}

components/page_load_metrics/browser/metrics_web_contents_observer_unittest.cc

@@ -16,6 +16,7 @@
 #include "components/page_load_metrics/browser/page_load_metrics_test_content_browser_client.h"
 #include "components/page_load_metrics/browser/page_load_tracker.h"
 #include "components/page_load_metrics/browser/test_metrics_web_contents_observer_embedder.h"
+#include "content/public/browser/back_forward_cache.h"
 #include "content/public/browser/navigation_handle.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/content_features.h"
@@ -174,6 +175,14 @@ class MetricsWebContentsObserverTest
     return empty;
   }
 
+  void CheckErrorNoIPCsReceivedIfNeeded(int count) {
+    // With BackForwardCache, page is kept alive after navigation.
+    // ERR_NO_IPCS_RECEIVED isn't recorded as it is reported during destruction
+    // of page after navigation which doesn't happen with BackForwardCache.
+    if (!content::BackForwardCache::IsBackForwardCacheFeatureEnabled())
+      CheckErrorEvent(ERR_NO_IPCS_RECEIVED, count);
+  }
+
   const std::vector<mojom::PageLoadTimingPtr>& updated_timings() const {
     return embedder_interface_->updated_timings();
   }
@@ -550,7 +559,7 @@ TEST_F(MetricsWebContentsObserverTest, DontLogAbortChains) {
   NavigateAndCommit(GURL(kDefaultTestUrl2));
   NavigateAndCommit(GURL(kDefaultTestUrl));
   histogram_tester_.ExpectTotalCount(internal::kAbortChainSizeNewNavigation, 0);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 2);
+  CheckErrorNoIPCsReceivedIfNeeded(2);
   CheckTotalErrorEvents();
 }
 
@@ -881,7 +890,7 @@ TEST_F(MetricsWebContentsObserverTest,
       page_load_metrics::internal::INVALID_NULL_FIRST_INPUT_TIMESTAMP, 1);
 
   CheckErrorEvent(ERR_BAD_TIMING_IPC_INVALID_TIMING, 1);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 1);
+  CheckErrorNoIPCsReceivedIfNeeded(1);
   CheckTotalErrorEvents();
 }
 
@@ -911,7 +920,7 @@ TEST_F(MetricsWebContentsObserverTest,
       page_load_metrics::internal::INVALID_NULL_FIRST_INPUT_DELAY, 1);
 
   CheckErrorEvent(ERR_BAD_TIMING_IPC_INVALID_TIMING, 1);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 1);
+  CheckErrorNoIPCsReceivedIfNeeded(1);
   CheckTotalErrorEvents();
 }
 
@@ -941,7 +950,7 @@ TEST_F(MetricsWebContentsObserverTest,
       page_load_metrics::internal::INVALID_NULL_LONGEST_INPUT_TIMESTAMP, 1);
 
   CheckErrorEvent(ERR_BAD_TIMING_IPC_INVALID_TIMING, 1);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 1);
+  CheckErrorNoIPCsReceivedIfNeeded(1);
   CheckTotalErrorEvents();
 }
 
@@ -971,7 +980,7 @@ TEST_F(MetricsWebContentsObserverTest,
       page_load_metrics::internal::INVALID_NULL_LONGEST_INPUT_DELAY, 1);
 
   CheckErrorEvent(ERR_BAD_TIMING_IPC_INVALID_TIMING, 1);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 1);
+  CheckErrorNoIPCsReceivedIfNeeded(1);
   CheckTotalErrorEvents();
 }
 
@@ -1010,7 +1019,7 @@ TEST_F(MetricsWebContentsObserverTest,
       1);
 
   CheckErrorEvent(ERR_BAD_TIMING_IPC_INVALID_TIMING, 1);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 1);
+  CheckErrorNoIPCsReceivedIfNeeded(1);
   CheckTotalErrorEvents();
 }
 
@@ -1049,7 +1058,7 @@ TEST_F(MetricsWebContentsObserverTest,
       1);
 
   CheckErrorEvent(ERR_BAD_TIMING_IPC_INVALID_TIMING, 1);
-  CheckErrorEvent(ERR_NO_IPCS_RECEIVED, 1);
+  CheckErrorNoIPCsReceivedIfNeeded(1);
   CheckTotalErrorEvents();
 }
 

content/browser/renderer_host/back_forward_cache_impl.cc

@@ -632,6 +632,11 @@ void BackForwardCacheImpl::PostTaskToDestroyEvictedFrames() {
                                 weak_factory_.GetWeakPtr()));
 }
 
+// static
+bool BackForwardCache::IsBackForwardCacheFeatureEnabled() {
+  return IsBackForwardCacheEnabled();
+}
+
 // static
 void BackForwardCache::DisableForRenderFrameHost(RenderFrameHost* rfh,
                                                  base::StringPiece reason) {

content/public/browser/back_forward_cache.h

@@ -28,6 +28,9 @@ class RenderFrameHost;
 // All methods of this class should be called from the UI thread.
 class CONTENT_EXPORT BackForwardCache {
  public:
+  // Returns true if BackForwardCache is enabled.
+  static bool IsBackForwardCacheFeatureEnabled();
+
   // Prevents the |render_frame_host| from entering the BackForwardCache. A
   // RenderFrameHost can only enter the BackForwardCache if the main one and all
   // its children can. This action can not be undone. Any document that is